de Serres F J, Overton L K, Sadler B M
Center for Life Sciences and Toxicology, Research Triangle Institute, Research Triangle Park, NC 27709.
Mutat Res. 1992 May;267(1):105-24. doi: 10.1016/0027-5107(92)90115-i.
Previous studies on X-ray-induced irreparable adenine-3 mutations (designated [ad-3]IR), induced in heterokaryon 12 of Neurospora crassa, demonstrated that they were not recessive and exhibited heterozygous effects in terms of markedly reduced linear growth rates (de Serres, 1965). Complementation tests with a series of tester strains carrying multilocus deletion mutations in the ad-3 and immediately adjacent genetic regions demonstrated that X-ray-induced irreparable mutations map, in the main part, as a series of overlapping multilocus deletion mutations that extend both proximally and distally into the immediately adjacent genetic regions, as well as into the 'X' region (a region of unknown, but essential function) between ad-3A and ad-3B (de Serres, 1968, 1989). Further studies (de Serres and Miller, 1988) have shown that the heterozygous effects of multilocus deletion mutations in the ad-3 region can be modified genetically and biochemically. In the present paper, the heterozygous effects of X-ray-induced multilocus deletion mutations of genotype ad-3A or ad-3B, induced in heterokaryon 12 (Webber and de Serres, 1965; de Serres, 1988, 1989), have been determined. These data show that 57.7% (15/26) of X-ray-induced multilocus deletion mutations covering the ad-3A locus have heterozygous effects, in terms of reduced linear growth rates, in forced dikaryons with a gene/point mutant at the ad-3B locus and 80.0% (20/25) in forced dikaryons with a multilocus deletion mutation covering the ad-3B locus. In addition, 35.1% (20/57) of X-ray-induced multilocus deletion mutations covering the ad-3B locus have heterozygous effects in forced dikaryons with a gene/point mutant at the ad-3A locus, and 100.0% (35/35) in forced dikaryons with a multilocus deletion mutation covering the ad-3A locus. These results demonstrate that the dominant or recessive characteristics of X-ray-induced specific-locus mutations resulting from multilocus deletion mutations are allele specific.
先前对在粗糙脉孢菌异核体12中诱导产生的X射线诱导的不可修复的腺嘌呤-3突变（命名为[ad-3]IR）的研究表明，它们不是隐性的，并且在显著降低的线性生长速率方面表现出杂合效应（德塞雷斯，1965年）。用一系列在ad-3及其紧邻的遗传区域携带多位点缺失突变的测试菌株进行互补试验表明，X射线诱导的不可修复突变在主要部分定位为一系列重叠的多位点缺失突变，这些突变向近端和远端延伸到紧邻的遗传区域，以及延伸到ad-3A和ad-3B之间的“X”区域（一个功能未知但必不可少的区域）（德塞雷斯，1968年、1989年）。进一步的研究（德塞雷斯和米勒，1988年）表明，ad-3区域中多位点缺失突变的杂合效应可以在遗传和生化方面进行修饰。在本文中，已经确定了在异核体12中诱导产生的基因型为ad-3A或ad-3B的X射线诱导的多位点缺失突变的杂合效应（韦伯和德塞雷斯，1965年；德塞雷斯，1988年、1989年）。这些数据表明，在具有ad-3B位点基因/点突变的强制双核体中，覆盖ad-3A位点的X射线诱导的多位点缺失突变中有57.7%（15/26）在降低线性生长速率方面具有杂合效应，在具有覆盖ad-3B位点的多位点缺失突变的强制双核体中这一比例为80.0%（20/25）。此外，在具有ad-3A位点基因/点突变的强制双核体中，覆盖ad-3B位点的X射线诱导的多位点缺失突变中有35.1%（20/57）具有杂合效应，在具有覆盖ad-3A位点的多位点缺失突变的强制双核体中这一比例为100.0%（35/35）。这些结果表明，由多位点缺失突变产生的X射线诱导的特定位点突变的显性或隐性特征是等位基因特异性的。
